Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities
Net income	$ 122,654	$ 129,176
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation of property, plant and equipment	126,112	122,921
Other amortization	19,134	17,896
Provision for credit losses	(506)	(20,642)
Loans originated, held for sale	(108,695)	(239,761)
Proceeds from sale of loans, held for sale	114,299	266,497
Gain on sales of investment securities, net and equity-method investment	(8,123)	(528)
Gain on sale of loans, net	(1,449)	(6,225)
Deferred income taxes	(14,683)	(7,355)
Share-based compensation expense	5,593	5,454
Allowance for equity funds used during construction	(4,879)	(4,568)
Other	(3,858)	(5,037)
Changes in assets and liabilities
Increase in accounts receivable and unbilled revenues, net	(101,641)	(41,884)
Increase in fuel oil stock	(119,890)	(43,681)
Decrease (increase) in regulatory assets	12,956	(17,731)
Increase in regulatory liabilities	11,288	5,824
Increase in accounts, interest and dividends payable	62,115	2,683
Change in prepaid and accrued income taxes, tax credits and utility revenue taxes	22,173	(1,818)
Decrease in defined benefit pension and other postretirement benefit plans liability	(2,698)	(3,834)
Change in other assets and liabilities	(55,260)	(39,800)
Net cash provided by operating activities	74,642	117,587
Cash flows from investing activities
Available-for-sale investment securities purchased	(366,177)	(1,101,289)
Principal repayments on available-for-sale investment securities	209,094	320,597
Proceeds from sale of available-for-sale investment securities	0	197,354
Purchases of held-to-maturity investment securities	0	(187,172)
Proceeds from repayments or maturities of held-to-maturity investment securities	7,932	38,401
Purchase of stock from Federal Home Loan Bank	(18,720)	(32,780)
Redemption of stock from Federal Home Loan Bank	15,520	31,460
Net decrease (increase) in loans held for investment	(212,744)	91,686
Proceeds from sale of residential loans	0	17,398
Capital expenditures	(147,749)	(148,414)
Contributions to low income housing investments	0	(6,478)
Other	15,813	7,805
Net cash used in investing activities	(497,031)	(771,432)
Cash flows from financing activities
Net increase in deposit liabilities	81,324	486,473
Net increase in short-term borrowings with original maturities of three months or less	70,019	31,257
Net increase in short-term borrowings from non-affiliates and affiliates with original maturities of three months or less	153,305	39,995
Repayment of short-term debt	0	(65,000)
Proceeds from issuance of long-term debt	67,312	191,487
Repayment of long-term debt	(15,030)	(51,989)
Withheld shares for employee taxes on vested share-based compensation	(3,079)	(2,002)
Common stock dividends	(76,602)	(74,311)
Preferred stock dividends of subsidiaries	(946)	(946)
Other	(318)	(2,037)
Net cash provided by financing activities	275,985	552,927
Net decrease in cash, cash equivalents and restricted cash	(146,404)	(100,918)
Cash, cash equivalents and restricted cash, beginning of period	311,462	358,979
Cash, cash equivalents and restricted cash, end of period	165,058	258,061
Less: Restricted cash	(5,386)	(10,618)
Cash and cash equivalents, end of period	$ 159,672	$ 247,443